1. Field of the Invention
This invention relates to a method for producing dinitro-diaza-alkanes and intermediate products thereof.
2. Description of the Prior Art
For several years, there have been known propellant powders which contain dinitro-diaza-alkanes as an energetic plasticizer, also known as a blasting oil, specifically 2,4-dinitro-2,4-diaza-pentane in this case, either alone or in mixture with other suitable alkanes (U.S. Pat. Nos. 4,476,322, 4,457,791).
It is in the nature of dinitro-diaza-alkanes that the propellant powders produced with them have combustion characteristics which are almost independent of temperature. This is a highly desirable property, which means that the ambient temperature has little or no influence on the maximum gas pressure evolved in the system in combustion of the propellant charge. Accordingly, propellant powders having combustion properties that are independent of temperature make it possible to utilize the maximum potential power of the system over a wide temperature range.
Extensive use of dinitro-diaza-alkanes for production of propellant powders having a suitably balanced temperature characteristic has been prevented in the past by the fact that dinitro-diaza-alkanes are difficult to synthesize and thus are expensive.
In the case of a known production process (U.S. Pat. No. 4,476,322 with additional citations therein), 2,4-dinitro-2,4-diaza-pentane is synthesized from dimethylurea or diethylurea. The urea is nitrated with nitric acid, and the nitration product is hydrolyzed to methylnitroamine or ethylnitroamine. The resulting nitroamines are condensed to 2,4-dinitro-2,4-diaza-pentane with the help of paraformaldehyde and sulfuric acid. By a similar method, 2,4-dinitro-2,4-diaza-hexane and 3,5-dinitro-3,5-diaza-heptane as well as mixtures of the three alkanes mentioned here can also be produced (Tartakofsky et al., Russian Chemical Bulletin, 1993, 42, 1916 ff). Synthesis from urea gives only a relatively low total yield, and the diethylurea used in this synthesis is very expensive. In addition, the nitrated urea compound is an extremely unstable, temperature-sensitive and acid-sensitive explosive intermediate product.
In another proposed method for synthesis of the aforementioned mixture of three dinitro-diaza-alkanes, methylamine or ethylamine is reacted with a chloroformic acid ester using sodium hydroxide solution to form an intermediate product which is then nitrated with nitric acid. The nitration product is reacted by means of ammonia and ethanol at reflux to form methylnitroamine or ethylnitroamine, which is then condensed to form the dinitro-diaza-alkanes as in the preceding method. In this process, the next-to-last step in the synthesis of the nitroamines is very complicated and time-intensive, so that it cannot be implemented on a large scale industrially.
The object of this invention is to provide a method of synthesis of dinitro-diaza-alkanes which can be carried out easily and economically on a large scale industrially without any great safety risks.
This object is achieved according to this invention with the method characterized in a combination of the following steps:
1. reacting a diester of a dicarboxylic acid with an alkylamine in an aqueous medium to yield the corresponding dialkyldiamid of the dicarboxylic acid;
2. nitrating the resulting dialkyldiamide by means of the usual nitration agents to form the corresponding dialkyldinitroamide of dicarboxylic acid;
3. reacting the resulting dialkyldinitroamide to form the corresponding alkylnitroamine by mixing the dialkyldinitroamide in an aqueous medium with methylamine and/or ethylamine, separating the resulting dimethyldiamide and/or diethyldiamide of the dicarboxylic acid, acidifying the remaining product and then extracting the alkylnitroamine from that; and
4. condensing the isolated alkylnitroamine to form the dinitro-diaza-alkanes in the known manner.
The method is further characterized in the following embodiments:
a. the process starts with a dialkyl ester of an aliphatic dicarboxylic acid, preferably oxalic acid;
b. the process starts with oxalic acid diethyl ester;
c. methylamine and/or ethylamine, preferably ethylamine, is used in the first step;
d. methylamine is used in the third step;
e. in the first step, the alkylamine in an aqueous solution is added gradually to the dialkyl ester at a temperature between 0xc2x0 C. and 80xc2x0 C. and the reaction product is filtered out after a secondary reaction time of 0.5 to 3 hours, preferably one to two hours;
f. in the second step lactic acid, nitric acid, acetic anhydride or dinitrogen pentoxide with or without a solvent is used as the nitration agent;
g. the dialkyldiamide is dissolved in nitric acid, and mixed with concentrated sulfuric acid at a temperature below 20xc2x0 C., then the reaction product is poured onto ice and then filtered or separated;
h. in the third step the remaining product is acidified with concentrated sulfuric acid, and then the alkylnitroamine is extracted with an organic solvent preferably with ether;
i. the fourth step begins with paraformaldehyde in the concentrated sulfuric acid to which alkylnitroamine is added gradually at a temperature between xe2x88x9220xc2x0 C. and +20xc2x0 C., then diluting with water and extracting with an organic solvent and finally washing the organic phases and removing the solvent;
j. the dimethyldiamide and/or diethyldiamide which is separated as a by-product in the third step is nitrated again in the second step and used in the third step to synthesize methylnitroamine and ethylnitroamine; and
k. in the second step dimethyldiamide and diethyldiamide are nitrated together, and the two reaction products are jointly reacted to form methylnitroamine and ethylnitroamine in the third step.
The invention is more broadly concerned with a method of synthesis of alkylnitroamines from alkylamines and esters, characterized by the following steps:
1. reacting a diester of a dicarboxylic acid with an alkylamine in an aqueous medium to yield the corresponding dialkyldiamide of the dicarboxylic acid;
2. nitrating the resulting dialkyldiamide by means of the usual nitration agents to form the corresponding dialkyldinitroamide of dicarboxylic acid; and
3. reacting the resulting dialkyldinitroamide to form the corresponding alkylnitroamine by mixing the dialkyldinitroamide in an aqueous medium with methylamine and/or ethylamine, separating the resulting dimethyldiamide and/or diethyldiamide of the dicarboxylic acid, acidifying the remaining product and then extracting the alkylnitroamine from that.